Tumor hypoxia is related to poor prognosis in several human tumors, treated with radiation therapy, surgery and chemotherapy - alone or in combination. The reasons are multiple. Radiation and many drugs are less effective on hypoxic cells. Additionally, altered gene expression that promotes angiogenesis, cell survival and metastasis may contribute. The long-term objectives of this work are to determine whether: (1) tumor hypoxia plays a role in chemoresistance (2) improved oxygenation can lead to better outcome in the adjuvant and metastatic setting. Clinical studies and pre-clinical investigation of hypoxia modification strategies are proposed. A novel model of micrometastatic disease for both the pre-angiogenic and post-angiogenic phases of growth will facilitate achievement of the objectives. Hypoxia is known to induce chemoresistance to many drugs, including doxorubicin (DOX). DOX will be the exemplary drug tested, both at the clinical and pre-clinical level. Specific aim 1, We will measure tumor hypoxia in patients with locally advanced breast cancer who are treated on a Phase I-II clinical trial, testing neoadjuvant thermochemotherapy for locally advanced breast cancer. The hypothesis is that tumor hypoxia will impact negatively on tumor response from this therapy. Specific aim 2, Using archival Breast SPORE banked tissue, from over 500 patients treated with DOX in the adjuvant setting, we will determine if hypoxia is correlated with chemoresistance. Specific aim 3, We will determine whether strategies to improve tumor PO2 (treatment with erythropoietin and or a unique metabolic method to acutely improve tumor PO2), in the presence or absence of interference with Her2/neu (Her2) signaling, will increase DOX responsiveness in Her2 positive and negative xenograft lines. The pre-clinical model of micrometastasis allows us to serially and simultaneously monitor tumor growth, hypoxia and angiogenesis. Growth in flank tumors will also be evaluated, which simulates how treatment modifications will affect patients with metastatic disease. If positive results were obtained they would pave the way for initiation of additional human clinical trials to test hypoxia modification strategies in combination with chemotherapy.